Add duplicate submission validation with captcha and automatic submission time tracking

[Copilot]

Summary

Implements duplicate submission validation and automatic submission time tracking for the freshman registration system as requested in the issue. When duplicate submissions are detected (based on email, phone, or student number), users are required to enter a captcha to proceed.

Changes Made

🔧 Schema Updates

• Added optional captcha field to JoinRequest schema for verification input
• Created new FreshmanRecord schema with submissionTime field for database storage
• Maintained backward compatibility with existing API calls

🛡️ Duplicate Detection Logic

The system now detects duplicate submissions by checking if any of these fields already exist:

• Email address
• Phone number
• Student number

When a duplicate is detected:

1. First attempt: Returns error message requesting captcha input
2. With captcha: Validates captcha (minimum 6 characters) before proceeding
3. Invalid captcha: Rejects submission with appropriate error message

⏰ Automatic Time Tracking

All new submissions automatically include a submissionTime field with the current timestamp. The existing auto-DDL system handles database schema migration seamlessly.

📝 Enhanced API Response

The API now returns additional information:

{
  "success": boolean,
  "result": FreshmanRecord | undefined,
  "error": string | undefined,
  "requiresCaptcha": boolean | undefined  // New field
}

Example Usage

Normal submission works unchanged:

POST /api/freshman
{
  "name": "张三",
  "email": "zhangsan@qq.com",
  "phone": "12345678901",
  // ... other fields
}

Duplicate submission requires captcha:

POST /api/freshman
{
  "name": "李四", 
  "email": "zhangsan@qq.com",  // Duplicate email
  "captcha": "abc123",         // Required for duplicates
  // ... other fields
}

Security & Compatibility

• Backward Compatible: Existing API calls continue working without modification
• Security Conscious: Captcha values are validated but not stored in database
• Error Messages: Proper Chinese language error messages for user feedback
• Type Safety: Full TypeScript support with proper schema validation

Testing

• ✅ TypeScript compilation successful
• ✅ Code passes all linting and formatting checks
• ✅ Cloudflare Workers dry-run deployment successful
• ✅ Logic validation tested with sample data

The implementation uses minimal, surgical changes while providing robust duplicate detection and time tracking functionality.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• sparrow.cloudflare.com
  • Triggering command: /usr/local/bin/node --no-warnings --experimental-vm-modules /home/REDACTED/work/serverless-active/serverless-active/node_modules/wrangler/wrangler-dist/cli.js deploy --dry-run (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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